package acwing._2LanQiao._13No13;
/**
 * @Project : AlgorithmLearning
 * @Package : ACWing._2LanQiao._13No13
 * @File : Q4402.java
 * @Author : WangRuoyu
 * @Date : 2023/3/30 17:22
 */

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class Q4402 {
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        String[] words = br.readLine().split(" ");
        long a = Long.parseLong(words[0]);
        long b = Long.parseLong(words[1]);
        long n = Long.parseLong(words[2]);

        long res = 0;

        long week = n / (5 * a + 2 * b);
        res += 7 * week;
        n %= (5 * a + 2 * b);
        if (n <= 5 * a) {
            res += (n + a - 1) / a;
        } else {
            res += 5 + (n - 5 * a + b - 1) / b;
        }
        System.out.println(res);
    }
}

